Brake shoe adjusting mechanism



Patented Dec. 2, 1952 BRAKE SHOE ADJUSTING MECHANISM Steve Schnell,Kirkwood, Mo., assigner to Wagner Electric Corporation, St. Louis, Mo.,a corporation of Delaware Application December 18, 1946, Serial No.716,987

(Cl. 18S-79.5)

7 Claims.

This invention relates to a brake mechanism and in its more specicaspects is directed to a device for automatically adjusting theclearance between a brake shoe and the cooperating drum.

The object of this invention is to provide a brake shoe adjustingmechanism for maintaining a substantially constant clearance duringdeenergized periods between the brake shoe and the cooperating brakedrum which is operative only after a predetermined wear of the frictionelement has occurred and which is inoperative at all other times. Themechanism is provided with a pivoted brake drum contacting member whichactuates the adjusting mechanism after a predetermined brake lining wearand re-positions the brake shoe to maintain said constant clearance.

In the drawings Figure 1 shows an elevational View, partly in section,of a portion of a brake assembly incorporating the invention;

Figure 2 is a sectional view taken substantially along the line 2 2 ofFigure 1; and

Figure 3 is a sectional view taken substantially along the line 3-3 ofFigure 1.

Referring now to the drawings, numeral l designates a backing plate onwhich a brake shoe 2 carrying a lining or friction element 2a ispivotally supported, as is well known in the art. 3 is a brake drum and4 is a brake applying motor mounted on backing plate I, all of which isconventional in the art.

An eccentric 5 is mounted in backing plate I on a pin and constitutes anadjustable fixed stop for brake shoe 2. Eccentric 5 is provided toinitially adjust the clearance between brake shoe 2 and drum 3 and todetermine the off position of brake shoe 2.

A lever 'l is pivoted to a pin 5 fixed in web il of shoe 2. Theunpivoted end of lever 'I is engaged and supported by eccentric 5. Abrake drum contacting member l is pivoted to lever 'I by means of a pinI I. Member lil is arranged in a suitable aperture i2 formed in thebrake shoe 2 to enable member i8 to engage drum 3 when the frictionelement 2a is sufficiently worn.

Lever 'l is provided with a serrated surface I3 which cooperates with alike serrated surface I4 on wedge I5. Spring I5 is provided to movewedge i 5 which may have a 10-20 taper toward the unpivoted end of leverl and reacts upon a suitable abutment (not shown) secured to web 8. Athrust member i8 is pivotally mounted on web 8 and tongue I'I formedthereon is disposed in slot I9 in wedge l5 to assist in maintainingwedge I5 aligned. Member I8 also absorbs the upward thrust from spring2|. This upward thrust of spring 2| maintains members I, I5, and I8 inposition during period of non-adjustment.

Member Ill is provided with a lever arm 20 which is engaged by the freeend of a leaf spring 2l secured at its other end to an abutment 22fastened on web 8. Leaf spring 2| rotates: member I0 in a clockwisedirection, as viewed in Figure 1, and tends to maintain it in the fullposition shown.

Referring now to the operation of the device and assuming that brakeshoe 2 and friction element 2a have been worn approximatelyfourthousandths of an inch, the shoe will be ready for adjustment. Theshoe will be adjusted outwardly approximately four-thousandths of aninch when the taper angle of wedge I5 is substantially sixteen degreesand the serration depth is substantially six-thousandths of an inch andwith the radius of brake shoe 2, the length of lever l, and the lengthof brake drum contacting member I0 suitably proportioned. When shoe 2 isnow moved outwardly by motor 4 into engagement with brake drum 3, thebrake drum contacting member I0 contacts brake drum 3. Lever l is not inengagement with eccentric 5 when brake shoe 2 engages the brake drum andthe distance between the unpivoted end of lever 1 and stop 5 is thensubstantially equal to the clearance between brake drum 3 and the drumengaging surface of friction element 2a. The rotative movement of thebrake drum in the direction of the arrow will, therefore, rotate `thebrake drum contacting member I0 about pin II. When the longitudinal axisof member I0 is aligned with the radii of shoe 2 and drum 3, lever `lwill have rotated clockwise about pin 9 producing maximum inwardmovement of lever 'I toward stop 5 and causing the serrated surfaces I3and Ii to be separated.

During the period of serration separation spring I6 will move wedge I5upward, as viewed in Figure 1, to the next serration positon. The upwardmovement of wedge I5 is limited to one serration because the tip of thesucceeding serration will prevent further upward movement of wedge I5.The clearance between the unpivoted end of lever 'I and stop 5 will,therefore, be reduced by approximately four-thousandths of an inch andAwhen spring 23 retracts brake shoe 2 to brake disengaged position, itwill be substantially fourthousandths of an inch closer to the drum. Asbrake shoe 2 retracts, leaf spring 2| will return the brake drumcontacting member I0 to the full lline position in Figure 1 and willalso lock the thrust'member I8, wedge I5 and lever 'I in engagement andno further adjustment will occur until the friction element 2a has againworn down four-thousandths of an inch.

Slot I2 in web 8 and the friction element receiving portion of brakeshoe 2 and friction element 2a shown in Figure l as of a size to permitthe brake drum contacting member I to go to the dotted line position I2in which position the unpivoted end of member I0 is disengaged from drum3. However, it may be desirable under some circumstances to narrow slotI2 to such an extent that it will limit the rotative movement of memberI0 to a position substantially that of I2 which is approximately theposition wherein the longitudinal axis of the brake drum contactingmember Il) is in substantial alignment with one of the radii of brakedrum 3.

Having fully described my invention, that which I cla'iin'as novel anddesire to protect by Letters Patent of thel United States is: Y

1. A brake mechanism comprising a drum, a brake shoe provided with alining engageable with said brake drum, an o position stop member, alever, one end thereof being pivoted to said shoe and the other endengaging said stop member when said lining is disengaged from Vthe drum,a brake drum contacting member pivoted to said lever at the unpivotedend thereof and contactable with the drum at a ,point ahead of a radiusof the drum which passes through said drum contacting member pivot pointafter a predetermined .lining Wear and arranged to travel through anarcuate path to a point beyond said drum radius upon contacting saiddrum, thereby moving the free end of said lever inwardly, means forbiasingV said drum contacting memberA to its rest position; and meansfor preventing the return of said lever end to its original positionwith respect to said shoe.

2. A brakeY adjusting mechanism comprising a brake drum, a brake shoeprovided with a lining engageable with said brake drum, an off positionstop member for said shoe, a lever, one end thereof pivoted to said shoeand the other end engaging said stop member when said lining isdisengaged from said drum, a pin secured in said lever near the otherend thereof, a brake drum contacting member rockably mounted on said pinand contactable with said drum ahead of a line passing through said pinand the center of said drum; a thrust member secured to said shoe; and aspring pressed wedge disposed between said thrust member and said leverfor holding said lever in adjusted position, said lever being adjustedby said contacting member when it is rocked about said pin after saidcontacting member engages said drum.

3. A brake mechanism comprising a brake drum, a brake shoe provided witha lining engageable with the brake drum and having a circumferentialslot therein, an oir position stop member for the brake shoe, a lever,one end thereof being pivoted to said brake shoe and the other endengaging said stop member when said lining is disengaged from the drum,a brake drum contacting member extending through said slot pivoted tosaid lever near the other end. thereof and contactable with sai-d drumat a point ahead of a line passing through the center of the drum andthrough the pivoting axis of said brake drum contacting member, saidbrake drum` contacting member contacting said drum after a predeterminedlining wear so that said drum will pivot said member for adjusting saidlever while said contact member is being rotated to drum disengagedposition, a thrust member secured to said shoe, a wedge disposed betweensaid thrust member and said lever, a spring anchored on said shoe andengaging said wedge for acting on said wedge for changing its positionbetween said lever and said thrust member when said brake drumcontacting member is: actuated by the brake drum; and means formaintaining said lever, wedge, and thrust member in operativeengagement.

4. A brake mechanism comprising a brake drum, a brake shoe provided witha lining engageable with the brake drum and having an elongatedcircumferential slot therein, an off position rstop member for the brakeshoe, a lever,

one end thereof being pivoted to said shoe and the other end engagingsaid stop member when said lining is disengaged from the drum, a pin insaid lever near the other end thereof, a brake drum contacting memberextending through said slot normally in operative position and rotatablymounted on said pin, said member contactable with said drum at a pointahead of a line passing through said pin and the center of said drumafter a predetermined lining wear, the drum rotating said member frominoperative position to a point on the other side of said line at whichpoint said member is disengaged from said drum, a thrust member securedto said shoe, a Wedge disposed between said thrust member and saidlever, a spring anchored on said shoe land engaging said wedge formoving said Wedge to a different position when said brake drumcontacting member actuated by the brake drum and is coaxial with saidline passing through said pin and the center of said drum; and anotherspring anchored to said shoe and engaging said brake drum contactingmember for returning said brake drum contacting member to inoperativeposition after said shoe is disengaged from the drum and for maintainingthe adjusted position of said lever relative to said stop member.

5. A brake mechanism comprising a brake shoe provided with a liningengageable with the brake drum and having an aperture in said lining andshoe elongated in the direction of movement of the drum, an off positionstop member for said brake shoe, a lever, one end thereof being pivotedto said shoe and the other end engaging said stop member when saidlining is disengaged from the brake drum, a brake drum contacting memberpivoted to said lever near the other end thereof extending through saidslot and contactable with said drum at a point ahead of a line passingthrough the point of pivoting of said member and the center of said drumafter a predetermined lining wear, said drum pivoting said member aboutthe pivot to drumdisengaged position when said lining is being engagedby said drum for adjusting the position of said lever, a thrust membersecured to said shoe, a wedge disposed between said lever and saidthrust member for maintaining the adjusted position of said leverrelative to the drum, the adjustment occurring when said contactingmember is coaxial with said line passing through the pivotal axis`thereof and through the center of said drum, a spring anchored on saidshoe and in engagement with said Wedge for moving said wedge to adiierent position when said brake drum contacting member is actuated bysaid drum, and a spring anchored to said shoe and in engagement withsaid contacting member for reversely moving the contacting member aftersaid shoe is disengaged from said drum.

6. A brake mechanism comprising a brake drum, a brake shoe provided witha lining each having an aligned elongated slot therein and engageablewith the brake drum, an off position stop member for the brake shoe, alever, one end thereof being pivoted to said shoe and the other endengaging said stop member when said lining is disengaged by the drum, apin secured in the unpivoted end of said lever, a brake drum contactingmember extending through said slot and normally in inoperative positionand supported on said pin and contactable With said drum at a. pointahead of a line passing through said pin and the center of said drumafter a predetermined lining Wear, said drum rotating said member aboutsaid pin from inoperative position to drum-disengaged position when saidlining is engaging said drum, said lever being adjusted during the timesaid brake drum contacting member is being rotated, a thrust member onsaid shoe, a Wedge disposed between said lever and said thrust member, aspring anchored to said shoe and in engagement with said Wedge formoving said Wedge to a diierent position when said brake drum contactingmember is being rotated by said drum; and spring means anchored to saidshoe and in engagement With said con- .tacting member for returning saidbrake drum contacting member to inoperative position after said liningis disengaged from the drum.

7. A brake mechanism comprising a brake drum, a brake shoe provided witha lining engageable With the brake drum, an off position stop member forsaid shoe, a lever, one end thereof being pivoted to said shoe and theother end engaging said stop member when said lining is disengaged fromthe drum, a pin secured to the unpivoted end of said lever; and a brakedrum contacting member pivoted to said pin and contactable With the drumafter a predetermined lining Wear at a point on said drum ahead of aline passing through the center of the drum and said pin and movable todrum disengaged position at a point beyond said line, said lever beingadjusted during the time said brake drum contacting member is beingpivoted by said drum.

STEVE SCHNELL.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 2,158,804 Schnell May 16, 19392,199,269 Page Apr. 30, 1940 Goepfrich Nov. 12, 1940

